Dyeing of wool with nonmetallized acid colors



Patented Apr. 11, 1944 DYEING F WOOL WITH NONMETALLIZED ACID COLORS Miles A. Dahlen and Harry F. Clapham, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 19, 1941,

. Serial No. 419,716

6 Claims. (01. s-.-54)

This invention relates to the dyeing of wool with acid colors, and especially to new processes and dyebath for this purpose which provide eco nomical exhaustion of the dyebaths, normally rapild dyeings. and negligible degradation of the woo In' the dyeing of'wool with acid colors, an optimum amount of acid in the dyebath is essential to attain satisfactory dyeings, such as good exhaustion of the dyebath and strong level dyeings in normal dyeing periods. Heretofore this amount of acid has been attained by adding sulfuric acid to the bath, but it is known that in the presence of sufiicient sulfuric acid to assure satisfactory exhaust, the pH value of the dyebath is between .5 and 2.5. Dyebaths having such pH values cause degradation or tendering of the fiber. Such dyebaths often contain about 2% to about 4% sulfuric acid and about to about 30% of Glaubers salt of the weight of the material to be treated. A prolonged boiling of about forty-five minutes to one hour is used to fix the dyes well and to assure levelness of dyeing. Such a prolongedboiling in acid solutions containing sulfuric acid in excess of 0.2% produces tendering or weakening of the fiber and higher concentrations of sulfuric acid have a relatively greater deleterious effect. that not more than about of sulfuric acid combines with the wool in solutions which have a pH value of 3 before immersion and about 6 0% to 80% combines when the sulfuric acid has a PE value of 2 before immersion of the fiber. In

both cases the pH value of the acid solution increases as the combination with the fiber takes place.

Acetic acid has been used instead of sulfuric acid and it has been used in coniunction'with sulfuric acid in dyebaths for dyeing with acid colors. The use of acetic acid instead of sulfuric acid is an improvement over the use ofsulfuric acid in so far as degradation of the wool is conamounts necessary to attain satisfactory exhaustion the pH value is in the range of 2.0 to 3.0 and Investigations have indicated I some degradation of the wool takes place. It is our present belief that acidification with sulfuric acid is presently employed in most commercial operations notwithstanding its deleterious effect on the wool because it works better in so far as the dyeing itself is concerned, but it is recognized as being desirable to provide dyebaths for acid dyes which exhaust satisfactorily, operate rapidly, produce level dyeing and do not deleteriously affect the fiber. It is among the objects of the present invention to provide new dyebaths for dyeing with acid colors. Another object of the invention is to provide new methods for dyeing acid dyes whereby economicaLexhaustiOn is realized within a pH value of the dyebath where the effect of the acid on the fiber is negligible. Other objects of the invention will be apparent from the following description. p

The objects of the invention are attained in general by adding hydroxy-acetic acid to the dyebath of a. non-metallized acid dye as the acidifying agent, and attaining thereby the optimum pH value for satisfactory dyeing, namely a. pH value of about 3.0 to about 3.5.- When thi pH value is attained by the addition of hydroxyacetic acid, it'has been discovered that the exhaustion of the bath compares favorably with.

Example 1 Adyebath was prepared by dissolving du Pont Anthratiuinone-Blue BN (C. I. 1054) and crystalline Glaubers salt in water in the proportion of 2 parts of the dye, 10 parts of Glauber's salt and 4000 parts of water. Hydroxyacetic acid (4 parts) was then added to give a pH value of 3.1.

A piece of wool goods was entered into the cold bath which was at about 25 0., the proportion of bath to wool being 1 part wool to 40 parts bath. The bath was gradually heated to bring it to theboil over a period of 30 minutes and then boiled for minutes to complete the dyeing. The dyed piece was removed, rinsed and dried. The resulting dyeing was level, well penetrated and of good tinctorial value. During the entire dyeing period the pH value of the dyebath was in the range of 3 to 4, where degradation of the wool is minimized.

The dyebath was tested for pH value before the wool was entered, five minutes after the wool was entered and at the end of the forty-five minute boiling, giving pH values of 3.1, 3.5 and 3.85, respectively. Exhaustion was 95% as shown by the well known standardized method of testing for exhaustion which consists of adding 3% of sulfuric acid to the used dyebath and a fresh amount of wool. The wool is boiled in the bath for 30 minutes. The relative amount of dye absorbed by the Wool indicates the amount of color remaining in the dyebath after the first dyeing and from this the completeness of exhaust of the color during the first dyeing can be estimated.

Example 2 A dyebath was made like that of Example 1 except that 7 parts of hydroxy-acetic acid were added to give a pH value of 3.0. A dyeing on wool was made in the same manner as described in Example 1 and the same tests were made on the dyebath. The resulting dyeing was level, well penetrated and of good tinctorial value.

The pH values of the dyebath at the start, five minutes after entering the wool and at the end of the dyeing were 3.0, 3.28 and 3.65, and the exhaustion test showed 97% exhaustion.

A similar dyebath except that it was acidified with sulfuric acid to a pH value of 3.26 contained about 0.28% sulfuric acid. At the end of five minutes after entering the wool, the pH value of dyeing, 2.3 at the end of five minutes, and 2.4 at the end of the dyeing period. The exhaustion was satisfactory in this dyeing, being 97%, but the pH was within the range where degradation of the wool takes place.

A dyebath was made like that used in Example 1 except that acetic acid was used instead of hydroxy-acetic acid to give a pH value of about 3.35. During a dyeing operation like that described in Example 1, the pH value of this bath increased to about 4 and about 80%-to 90% exhaustion was obtained. The dyeing obtained under these conditions was level and well penetrated but the exhaust was not economical even though an excessive amount of acetic acid was used. As an example of the use of formic acid. a dyebath was used'similar to that described in Example 1,' except that formic acid was used instead of hydroxy-acetic acid as the exhausting agent for dyeing acid colors. During a dyeing operation like that described in Example 1. the pH value of this bath ranged between 2.5 and 3. The dyeing was level, well penetrated and showed a good exhaust but the pH of the dyebath was as level dyeing acid colors which were commonly dyed heretofore from baths which were acidified with sulfuric acid as well as those which normally dye more rapidly. As illustrative of such dyes are mentioned Pontacyl Light Yellow QX (CI. 639) du Pont Orange G (C. I. 27 Pontacyl Carmine 2G (C. I. 31), Pontacyl Blue Black SX (C. I. 246) du Pont Orange II Concentrated (C. I, 151), du Pont Milling Red SWB (C.'I. 430), du Pont Brilliant Milling Green B Conc. (C. I. 66"!) and Pontacyl W001 Blue BL (C. I. 833).

As the pH values of dyebaths increase during dyeing, the speed of dyeing generally decreases. While more level dyeing ordinarily is associated with slower rates of dyeing, it is sometimes desirable to vary the pH value of the dyebath toward the acid side during the dyeing. This may be done without harming the goods by starting with a dyebath having any optimum pH value within the described range and then adding hydroxy-acetic acid during the dyeing in appropriate amounts to maintain a constant pH or lower the pH value.

From the foregoing disclosure it will be recognized that the invention is susceptible of modification without departing from the spirit and scope thereof and it is to be understood that the invention is not restricted to the specific illustrations thereof herein set forth.

We claim:

l. A dyebath for dyeing wool comprising essentially a water solution of a non-metallized acid wool dye and sufficient hydroxy-acetic acid to give the bath a pH value of about 3 to about 3.5.

2. A dyebath for dyeing wool comprising essentially a water solution of a non-metallized acid dye and containing about 5% to about 40% of crystalline Glaubers salt and sufficient hydroxy-acetic acid to give the mixture a pH value of about 3.0 to about 3.5.

3. In the process of dyeing wool by the action of a water solution of a nonmetallized acid dye, the step which comprises acidifying the solution of the dye to a pH value of about 3 to about 3.5 solely by adding hydroxy-acetic acid.

4. In the process of dyeing wool by the action of a water solution of a non-metalliz ed acid dye which contains Glaubers salt, the step which comprises acidifying the said solution to a pH value of about 3 to about 3.5 solely by adding 

